Nowadays, the on-chip operating voltages are generally lower than the voltage applied externally to the chip. Therefore, integrated voltage regulators are required on the chip in order to reduce the external voltage. The voltage regulators may be based, for example, on N-channel MOS technology. In order to be able to sufficiently increase the voltage at the gate of the output transistor—in the form of an NMOS transistor—of the voltage regulator, such series regulators additionally have a charge pump. In comparison with a PMOS transistor, an NMOS transistor as output transistor advantageously affords better suppression of the input voltage and lower sensitivity in the event of load fluctuations. Such voltage regulators may be in the form of three-point regulators, for example, although the voltage at the output of the voltage regulator has a certain ripple. With the aid of a continuous regulator, however, this ripple can be reduced and the voltage regulation can thus be improved. In principle, such circuits, which are also known by the designation low-drop voltage regulators, are designed for a particularly low voltage drop between the input and output. However, for this reason, it is disadvantageously not possible for the voltage regulator to start up independently.
The problem of the voltage regulator has hitherto been solved using a PMOS output transistor whose suppression of the input voltage and whose load behavior do not, however, satisfy the requirements. In addition, the high switch-on voltage spikes can no longer be tolerated in present-day technologies.